Numerical Study of Large-Scale Control in Compressible Turbulent Channel Flows

Direct numerical simulations in a fully developed compressible turbulent channel flows have been carried out using the large-scale control of large vortical structures along streamwise direction. Effectiveness of the control at Mach number, \(Ma = 1.5\) and Reynolds number \(Re_b = 3000\) is studied for different amplitudes and wavelengths of forcing. The large-scale control concentrates the turbulent kinetic energy in certain regions near the walls and it can be observed in \(y-z\) plane of the channel. These high turbulent kinetic energy regions are also the regions of high streamwise vorticity as well. The control reduces the wall-normal velocity fluctuations near the walls for all the cases but, on the other hand, Reynolds shear stresses are reduced for drag reduction cases and are increased for the case where drag increases. The skin-friction drag reduction(DR) of around \(7\%\) is achieved in the present study while, for the case with high strength vortical structures, the skin-friction drag increases.